As audio and video compression technology improves and player capacity rises, digital playback equipment is approaching ubiquity in everyday life. Portable digital music players, such at the Microsoft Zune player, can now be found everywhere. Additionally, listeners utilize car and home stereo systems when not listening to portable players.
Each of these listening environments is susceptible to noise from outside the playback system. Background noise, such as extraneous conversation, traffic noise, construction noise, or road or air travel noise, can make listening to music on a player or system difficult, if not impossible. And while a user can attempt to compensate for noise using his or her volume control, such an active solution is unpalatable to many, who would prefer their listening or viewing experience be more passive.
Existing techniques attempt to address these issues by providing automatic, finer-grained amplification (or “gain”) which changes to compensate for background noise, in order that a listener/viewer may enjoy his or her media consistently without being required to adjust the volume him or herself.
However, many existing volume compensation techniques suffer from inaccurate or overly-complex models of compensation to be particularly effective. In one example, existing techniques perform compensation based on comparisons of the amount of energy or intensity in the played signal to the energy contained in the background noise against which the compensation is to be performed. These techniques, while easy to implement, are unfortunately not optimal from a listener's perspective. In particular, these intensity-based techniques ignore essential inconsistencies in the way the human ear perceives additional sounds. For example, research has shown that two pitches of a given energy will sound louder to a listener if they are farther apart in frequency than if they are closer together. Existing compensation techniques and systems which rely solely on measures of energy cannot recognize a difference in these scenarios, however, and will therefore exhibit unpredictable and annoying results to a listener.
At the other end of the spectrum from these energy-based techniques are certain techniques which attempt to model the human hearing mechanism at a very high level of precision in order to provide for proper compensation. These techniques, while more cognizant of how increased volume is perceived by a listener, oftentimes rely on overly-complex breakdowns of audio, as well as utilize multiple perceptual models. What results is a great deal of calculation for each block of audio for which compensation is applied, in an effort to measure and exactly correct for numerous background sounds. This is undesirable as such an amount of calculation may be undesirable for existing players; extraneous computation can slow down responsiveness of playback equipment and can also unnecessarily lower battery life. Additionally, various existing techniques attempt to provide compensation at a very low granularity level, such that different levels of gain are applied for different frequencies of an audio signal. In addition to again requiring more computation than may be desired, such systems and techniques can result in compensated-for audio that may sound strange to a listener.
What is needed is a system for providing efficient compensation for background and other extraneous noise during playback, but which does not require overly-complex computation.